Field of the Technology
The present disclosure is directed to the field of air hardenable, shock-resistant steel alloys and articles including such alloys.
Description of the Background of the Technology
The present disclosure relates to novel air hardenable steel alloys that exhibit favorable strength, hardness, and toughness. The air hardenable steel alloys according to the present disclosure may be used, for example, to provide blast and/or shock protection for structures and vehicles, and also may be included in various other articles of manufacture. The present disclosure further relates to methods of processing certain steel alloys that improve resistance to residual and dynamic deformation and fragmentation associated with blast events.
Current materials used for blast or shock protection are predominantly Class 2 Rolled Homogeneous Armor (RHA) steels, under U.S. Military Specification MIL-DTL-12506J, and other mild steels intended for use in areas where maximum resistance to high rates of shock loading is required and where resistance to penetration by armor piercing ammunition is of secondary importance. The Class 2 RHA steels are water quenched and tempered to a maximum hardness of 302 HBW (Brinell Hardness Number) to impart ductility and impact resistance. This class of RHA steels is therefore principally intended for use as protection against anti-tank land mines, hand grenades, bursting shells, and other blast-producing weapons. Class 2 RHA steels specified according to MIL-DTL-12560J, and other mild steels, however, typically lack high strength and hardness to significantly resist residual and dynamic deformation and fragmentation associated with blast events.
Class 2 RHA steels are typically low alloy carbon steels that attain their properties via heat treating (austenitizing), water quenching, and tempering. Water quenching may be disadvantageous because it can result in excessive distortion of and residual stress generation in the steel. Water quenched steels also may exhibit large heat affected zones (HAZ) after welding. In addition, water quenched steels require an additional heat treatment after hot forming, followed by water quenching and tempering, to restore desired mechanical properties.
Accordingly, it would be advantageous to provide a steel alloy that exhibits higher strength and high ductility and toughness, as compared with Class 2 RHA low alloy carbon steels, that can attain desired mechanical properties required to reduce dynamic and residual deformation occurring in a blast event, and that eliminates or reduces problems associated with water quenching of Class 2 RHA materials.